The purpose of the present invention lies in novel 2',3'-dideoxy purine nucleosides represented by general formulae [I] and/or [II] and the processes for the preparation thereof. ##STR2## (wherein X indicates a nitrogen atom or carbon atom, and R.sub.1, R.sub.2 and R.sub.3 indicate each independently any of hydrogen atom, hydroxyl group, amino group, alkyl group, halogen atom, alkoxy group and mercapto group). ##STR3## (wherein Y indicates a nitrogen atom or carbon atom, and R.sub.4 and R.sub.5 indicate each independently any of hydrogen atom, hydroxyl group, amino group, alkyl group, halogen atom, alkoxy group and mercapto group).
Existing 2',3'-dideoxy nucleosides such as 2',3'-dideoxycytidine (hereinafter referred to as DDC), 2',3'-dideoxyadenosine (hereinafter referred to as DDA) and 2',3'-dideoxyinosine (hereinafter referred to as DDI) have the antiviral property and, because of remarkable effect particularly as antiretroviral agents, they are expected as anti-HIV agents. There are however problems in the aspect of the side effect of said compounds to the human body.
Namely, DDC causes a hindrance to peripheral nerves and DDA and DDI exhibit a toxicity to bone marrows.
Moreover, with 3'-azidethymidine (hereinafter referred to as AZT) being recognized currently as an only therapeutic drug for AIDS, the toxicity to bone marrows is found (N. Engl, J. Med., 316, 557, 1987; idid., 317, 185, 1987; Nature, 325, 773, 1987).
The subject of the invention is to find novel 2',3'-dideoxy nucleosides useful as medicines having the antiviral property, in particular antiretroviral property by overcoming said problems of known 2',3'-dideoxy nucleosides such as DDC, DDA, DDI and AZT.
The inventors have synthesized novel 2',3'-dideoxy purine nucleosides by linking 2,3-dideoxyribose to purine bases or purine base analogs modified with various atoms or functional groups (i.e. hydrogen atom, hydroxyl group, amino group, alkyl group, halogen atom, alkoxy group, mercapto group, etc.) through the action of microorganism and have found that the problems of conventionally known 2',3'-dideoxy nucleosides (DDC, DDA DDI, AZT, etc ) aforementioned can be overcome by using these compounds independently or using them together with conventionally known 2',3'-dideoxy nucleosides (DDC, DDA, DDI, AZT, etc.).